1. Field of the Invention
The invention relates to a minicamera for the detection of at least a composite .beta. and .gamma. nuclear radiation, or a .gamma. nuclear radiation associated with conversion electrons assimilated with a .beta. radiation, emitted by a radioisotope present in a body, its image pick-up head comprising a .beta. radiation collimator which is transparent to the .gamma. radiation, a scintillator and a photodetector assembly.
It is preferably used for the detection of a composite .beta. and .gamma. radiation emitted by a tracer radioisotope already assimilated by an organism, in which case it is intended to be applied against the incision made in said organism in the course of a surgical operation; the image pick-up head is then provided with a protective diaphragm. In this case it concerns a surgical camera.
2. Description of the Related Art
Specialist technical literature describes minicameras which form an image of molecules marked by pure .beta. emitters (molecular biology) or which detect the presence of .beta. radiation (beam study, impact research in particle physics).
The role of tracers has become of prime importance in medicine. It is notably possible to mark cancerous tumors by means of the radioisotope .sup.131 I which belongs to the family of markers emitting .beta. and .gamma. simultaneously. The .beta. radiation emitted by .sup.131 I has the property that it has a very limited interaction mean free path within the tissues, i.e. of the order of from 1 to 2 mm, considering its mean energy of a few hundreds of keV. The idea underlying the invention is the aim to detect this .beta. radiation emitted by a marked cancerous tissue, which is possible only during a surgical operation consisting of the excision of the cancerous tumor, in the absence of which the presence of healthy tissues covering the cancerous tissues would prevent any detection of this .beta. radiation inevitably absorbed by these healthy tissues. The exact technical problem to be solved at this stage is the elimination of the .gamma. radiation which accompanies the .beta. radiation and whose resultant detection signal has an amplitude which is substantially higher than that of the .beta. radiation.